Thought blocking (also known as ), a phenomenon that occurs in people with psychiatric illnesses (usually schizophrenia), occurs when a person's speech is suddenly interrupted by silences that may last a few seconds to a minute or longer. When the person begins speaking again, after the block, they will often speak about a subject unrelated to what was being discussed when blocking occurred. It is described as being experienced as an unanticipated, quick and total emptying of the mind. People with schizophrenia commonly experience thought blocking and may comprehend the experience in peculiar ways. For example a person with schizophrenia might remark that another person has removed their thoughts from their brain.

When doctors diagnose thought blocking, it is important that they consider other causes of pauses in speech and expression, such as petit mal seizures, aphasia, hesitation brought on by anxiety, or slow thought processes. When looking for schizophrenia they may look for thought blocking. It is a common issue with schizophrenia patients.

In considering whether an individual has thought disorder, patterns of their speech are closely observed. Although it is normal to exhibit some of the following during times of extreme stress (e.g. a cataclysmic event or the middle of a war) it is the degree, frequency, and the resulting functional impairment that leads to the conclusion that the person being observed has a thought disorder.

- "Alogia" (also "poverty of speech") – A poverty of speech, either in amount or content; it can occur as a negative symptom of schizophrenia.

- "Blocking" – An abrupt stop in the middle of a train of thought; the individual may or may not be able to continue the idea. This is a type of formal thought disorder that can be seen in schizophrenia.

- "Circumstantiality" (also "circumstantial thinking", or "circumstantial speech") – An inability to answer a question without giving excessive, unnecessary detail. This differs from tangential thinking, in that the person does eventually return to the original point.

- "Clanging" or "Clang association" – a severe form of flight of ideas whereby ideas are related only by similar or rhyming sounds rather than actual meaning. This may be heard as excessive rhyming and/or alliteration. e.g. "Many moldy mushrooms merge out of the mildewy mud on Mondays." "I heard the bell. Well, hell, then I fell." It is most commonly seen in bipolar affective disorder (manic phase), although it is often observed in patients with primary psychoses, namely schizophrenia and schizoaffective disorder.

- "Derailment" (also "loose association" and "knight's move thinking") – Thought and/or speech move, either spontaneously or in response to an internal stimulus (distinguishing derailment from "distractible speech," "infra"), from the topic's track onto another which is obliquely related or unrelated. e.g. "The next day when I'd be going out you know, I took control, like uh, I put bleach on my hair in California."

- "Distractible speech" – During mid speech, the subject is changed in response to an external stimulus. e.g. "Then I left San Francisco and moved to... where did you get that tie?"

- "Echolalia" – Echoing of another's speech that may only be committed once, or may be continuous in repetition. This may involve repeating only the last few words or last word of the examiner's sentences. This can be a symptom of Tourette's Syndrome. e.g. "What would you like for dinner?", "That's a good question. "That's a good question". "That's a good question". "That's a good question"."

- "Evasive interaction" – Attempts to express ideas and/or feelings about another individual come out as evasive or in a diluted form, e.g.: "I... er ah... you are uh... I think you have... uh-- acceptable erm... uh... hair."

- "Flight of ideas" – a form of formal thought disorder marked by abrupt leaps from one topic to another, albeit with discernable links between successive ideas, perhaps governed by similarities between subjects or, in somewhat higher grades, by rhyming, puns, and word plays (clang associations), or innocuous environmental stimuli – e.g., the sound of birds chirping. It is most characteristic of the manic phase of bipolar illness.

- "Illogicality" – Conclusions are reached that do not follow logically (non-sequiturs or faulty inferences). e.g. "Do you think this will fit in the box?" draws a reply like "Well duh; it's brown, isn't it?"

- "Incoherence (word salad)" – Speech that is unintelligible because, though the individual words are real words, the manner in which they are strung together results in incoherent gibberish, e.g. the question "Why do people comb their hair?" elicits a response like "Because it makes a twirl in life, my box is broken help me blue elephant. Isn't lettuce brave? I like electrons, hello please!"

- "Loss of goal" – Failure to follow a train of thought to a natural conclusion. e.g. "Why does my computer keep crashing?", "Well, you live in a stucco house, so the pair of scissors needs to be in another drawer."

- "Neologisms" – New word formations. These may also involve elisions of two words that are similar in meaning or in sound. e.g. "I got so angry I picked up a dish and threw it at the geshinker."

- "Perseveration" – Persistent repetition of words or ideas even when another person attempts to change the topic. e.g. "It's great to be here in Nevada, Nevada, Nevada, Nevada, Nevada." This may also involve repeatedly giving the same answer to different questions. e.g. "Is your name Mary?" "Yes." "Are you in the hospital?" "Yes." "Are you a table?" "Yes." Perseveration can include palilalia and logoclonia, and can be an indication of organic brain disease such as Parkinson's.

- "Phonemic paraphasia" – Mispronunciation; syllables out of sequence. e.g. "I slipped on the lice and broke my arm."

- "Pressure of speech" – Unrelenting, rapid speech without pauses. It may be difficult to interrupt the speaker, and the speaker may continue speaking even when a direct question is asked.

- "Self-reference" – Patient repeatedly and inappropriately refers back to self. e.g. "What's the time?", "It's 7 o'clock. That's my problem."

- "Semantic paraphasia" – Substitution of inappropriate word. e.g. "I slipped on the coat, on the ice I mean, and broke my book."

- "Stilted speech" – Speech characterized by the use of words or phrases that are flowery, excessive, and pompous. e.g. "The attorney comported himself indecorously."

- "Tangentiality" – Wandering from the topic and never returning to it or providing the information requested. e.g. in answer to the question "Where are you from?", a response "My dog is from England. They have good fish and chips there. Fish breathe through gills."

- "Word approximations" – Old words used in a new and unconventional way. e.g. "His boss was a ."

In psychiatry, thought withdrawal is the delusional belief that thoughts have been 'taken out' of the patient's mind, and the patient has no power over this. It often accompanies thought blocking. The patient may experience a break in the flow of their thoughts, believing that the missing thoughts have been withdrawn from their mind by some outside agency. This delusion is one of Schneider's first rank symptoms for schizophrenia. Because thought withdrawal is characterized as a delusion, according to the DSM-IV TR it represents a positive symptom of schizophrenia.

The concept of thought disorder has been criticized as being based on circular or incoherent definitions. For example, thought disorder is inferred from disordered speech, based on the assumption that disordered speech arises because of disordered thought. Incoherence, or word salad, refers to speech that is unconnected and conveys no meaning to the listener.

Furthermore, although thought disorder is typically associated with psychosis, similar phenomena can appear in different disorders, potentially leading to misdiagnosis—for example, in the case of incomplete yet potentially fruitful thought processes.

It has been suggested that individuals with autism spectrum disorders (ASD) display language disturbances like those found in schizophrenia; a 2008 study found that children and adolescents with ASD showed significantly more illogical thinking and loose associations than control subjects. The illogical thinking was related to cognitive functioning and executive control; the loose associations were related to communication symptoms and to parent reports of stress and anxiety.

In psychology, alogia (Greek ἀ-, “without”, and λόγος, “speech”), or poverty of speech, is a general lack of additional, unprompted content seen in normal speech. As a symptom, it is commonly seen in patients suffering from schizophrenia, and is considered a negative symptom. It can complicate psychotherapy severely because of the considerable difficulty in holding a fluent conversation.

Alogia is often considered a form of aphasia, which is a general impairment in linguistic ability. It often occurs with intellectual disability and dementia as a result of damage to the left hemisphere of the brain. People can revert to alogia as a way of reverse psychology, or avoiding questions.

Individuals with schizophrenia may experience hallucinations (most reported are hearing voices), delusions (often bizarre or persecutory in nature), and disorganized thinking and speech. The last may range from loss of train of thought, to sentences only loosely connected in meaning, to speech that is not understandable known as word salad. Social withdrawal, sloppiness of dress and hygiene, and loss of motivation and judgment are all common in schizophrenia.

Distortions of self-experience such as feeling as if one's thoughts or feelings are not really one's own to believing thoughts are being inserted into one's mind, sometimes termed passivity phenomena, are also common. There is often an observable pattern of emotional difficulty, for example lack of responsiveness. Impairment in social cognition is associated with schizophrenia, as are symptoms of paranoia. Social isolation commonly occurs. Difficulties in working and long-term memory, attention, executive functioning, and speed of processing also commonly occur. In one uncommon subtype, the person may be largely mute, remain motionless in bizarre postures, or exhibit purposeless agitation, all signs of catatonia. People with schizophrenia often find facial emotion perception to be difficult. It is unclear if the phenomenon called "thought blocking", where a talking person suddenly becomes silent for a few seconds to minutes, occurs in schizophrenia.

About 30 to 50 percent of people with schizophrenia fail to accept that they have an illness or comply with their recommended treatment. Treatment may have some effect on insight.

People with schizophrenia may have a high rate of irritable bowel syndrome but they often do not mention it unless specifically asked. Psychogenic polydipsia, or excessive fluid intake in the absence of physiological reasons to drink, is relatively common in people with schizophrenia.

Schizophrenia is often described in terms of positive and negative (or deficit) symptoms. "Positive symptoms" are those that most individuals do not normally experience, but are present in people with schizophrenia. They can include delusions, disordered thoughts and speech, and tactile, auditory, visual, olfactory and gustatory hallucinations, typically regarded as manifestations of psychosis. Hallucinations are also typically related to the content of the delusional theme. Positive symptoms generally respond well to medication.

"Negative symptoms" are deficits of normal emotional responses or of other thought processes, and are less responsive to medication. They commonly include flat expressions or little emotion, poverty of speech, inability to experience pleasure, lack of desire to form relationships, and lack of motivation. Negative symptoms appear to contribute more to poor quality of life, functional ability, and the burden on others than positive symptoms do. People with greater negative symptoms often have a history of poor adjustment before the onset of illness, and response to medication is often limited.

The validity of the positive and negative construct has been challenged by factor analysis studies observing a three dimension grouping of symptoms. While different terminology is used, a dimension for hallucinations, a dimension for disorganization, and a dimension for negative symptoms are usually described.

Alogia is characterized by a lack of speech, often caused by a disruption in the thought process. Usually, an injury to the left hemisphere of the brain will cause alogia to appear in an individual. In conversation, alogic patients will reply very sparsely and their answers to questions will lack spontaneous content; sometimes, they will even fail to answer at all. Their responses will be brief, generally only appearing as a response to a question or prompt.

Apart from the lack of content in a reply, the manner in which the person delivers the reply is affected as well. Patients affected by alogia will often slur their responses, and not pronounce the consonants as clearly as usual. The few words spoken usually trail off into a whisper, or are just ended by the second syllable. Studies have shown a correlation between alogic ratings in individuals and the amount and duration of pauses in their speech when responding to a series of questions posed by the researcher.

The inability to speak stems from a deeper mental inability that causes alogic patients to have difficulty grasping the right words mentally, as well as formulating their thoughts. A study investigating alogiacs and their results on the category fluency task showed that people with schizophrenia who exhibit alogia display a more disorganized semantic memory than controls. While both groups produced the same number of words, the words produced by people with schizophrenia were much more disorderly and the results of cluster analysis revealed bizarre coherence in the alogiac group.

Derealization can accompany the neurological conditions of epilepsy (particularly temporal lobe epilepsy), migraine, and mild head injury. There is a similarity between visual hypo-emotionality, a reduced emotional response to viewed objects, and derealization. This suggests a disruption of the process by which perception becomes emotionally coloured. This qualitative change in the experiencing of perception may lead to reports of anything viewed being unreal or detached.

Derealization can also manifest as an indirect result of certain vestibular disorders such as labyrinthitis. This is thought to result from the experience of anxiety precipitated by the functional disparity that arises between the ability to reconcile external stimuli relative to motion and equilibrioception that are compromised by vestibular dysfunction with the internal perceptions and expectations regarding the physical environment.

An alternative explanation holds that a possible effect of vestibular dysfunction includes responses in the form of the modulation of noradrenergic and serotonergic activity due to a misattribution of vestibular symptoms to the presence of imminent physical danger resulting in the experience of anxiety or panic, which subsequently generate feelings of derealization.

Cannabis, psychedelics, dissociatives, antidepressants, caffeine, nitrous oxide, albuterol, and nicotine can all produce feelings resembling derealization, particularly when taken in excess. It can result from alcohol withdrawal or benzodiazepine withdrawal. Opiate withdrawal can also cause feelings of derealization.

Derealization can also be a symptom of severe sleep disorders and mental disorders like depersonalization disorder, borderline personality disorder, bipolar disorder, schizophrenia, dissociative identity disorder, and anxiety disorders.

Interoceptive exposure can be used as a means to induce derealization, as well as the related phenomenon depersonalization.

Derealization (sometimes abbreviated as DR) is an alteration in the perception or experience of the external world so that it seems unreal. Other symptoms include feeling as though one's environment is lacking in spontaneity, emotional colouring, and depth. It is a dissociative symptom of many conditions.

Derealization is a subjective experience of unreality of the outside world, while depersonalization is sense of unreality in one's personal self, although most authors currently do not regard derealization (surroundings) and depersonalization (self) as separate constructs.

Chronic derealization may be caused by occipital–temporal dysfunction. These symptoms are common in the population, with a lifetime prevalence of up to 5% and 31–66% at the time of a traumatic event.

People with psychosis normally have one or more of the following:

- hallucinations

- delusions

- catatonia

- thought disorder.

Impairments in social cognition also occur.

A hallucination is defined as sensory perception in the absence of external stimuli. Hallucinations are different from illusions, or perceptual distortions, which are the misperception of external stimuli. Hallucinations may occur in any of the senses and take on almost any form, which may include simple sensations (such as lights, colors, tastes, and smells) to experiences such as seeing and interacting with fully formed animals and people, hearing voices, and having complex tactile sensations.

Auditory hallucinations, particularly experiences of hearing voices, are the most common and often prominent feature of psychosis. Hallucinated voices may talk about, or to, the person, and may involve several speakers with distinct personalities. Auditory hallucinations tend to be particularly distressing when they are derogatory, commanding or preoccupying. However, the experience of hearing voices need not always be a negative one. One research study has shown that the majority of people who hear voices are not in need of psychiatric help. The Hearing Voices Movement has subsequently been created to support voice hearers, regardless of whether they are considered to have a mental disorder or not.

Psychotic symptoms are often missed in psychotic depression, either because patients do not think their symptoms are abnormal or they attempt to conceal their symptoms from others. On the other hand, psychotic depression may be confused with schizoaffective disorder. Due to overlapping symptoms, differential diagnosis includes also dissociative disorders.

Thought insertion is defined by the ICD-10 as feeling as if one's thoughts are not one's own, but rather belong to someone else and have been inserted into one's mind. The person experiencing thought insertion will not necessarily know where the thought is coming from, but is able to distinguish between their own thoughts and those inserted into their minds. However, patients do not experience all thoughts as inserted, only certain ones, normally following a similar content or pattern. This phenomenon is classified as a delusion. A person with this delusional belief is convinced of the veracity of their beliefs and is unwilling to accept such diagnosis.

Thought insertion is a common symptom of psychosis and occurs in many mental disorders and other medical conditions. However, thought insertion is most commonly associated with schizophrenia. Thought insertion, along with thought broadcasting, thought withdrawal, thought blocking and other first rank symptoms, is a primary symptom and should not be confused with the delusional explanation given by the respondent. Although normally associated with some form of psychopathology, thought insertion can also be experienced in those considered nonpathological, usually in spiritual contexts, but also in culturally influenced practices such as mediumship and automatic writing.

Examples of thought insertion:

"She said that sometimes it seemed to be her own thought 'but I don't get the feeling that it is'. She said her 'own thoughts might say the same thing', 'but the feeling isn't the same', 'the feeling is that it is somebody else's'"

"I look out the window and I think that the garden looks nice and the grass looks cool, but the thoughts of Eamonn Andrews come into my mind. There are no other thoughts there, only his. He treats my mind like a screen and flashes thoughts onto it like you flash a picture"

"The subject has thoughts that she thinks are the thoughts of other people, somehow occurring in her own mind. It is not that the subject thinks that other people are making her think certain thoughts as if by hypnosis or psychokinesis, but that other people think the thoughts using the subject's mind as a psychological medium."

Individuals with psychotic depression experience the symptoms of a major depressive episode, along with one or more psychotic symptoms, including delusions and/or hallucinations. Delusions can be classified as mood congruent or incongruent, depending on whether or not the nature of the delusions is in keeping with the individual's mood state. Common themes of mood congruent delusions include guilt, persecution, punishment, personal inadequacy, or disease. Half of patients experience more than one kind of delusion. Delusions occur without hallucinations in about one-half to two-thirds of patients with psychotic depression. Hallucinations can be auditory, visual, olfactory (smell), or haptic (touch), and are congruent with delusional material. Affect is sad, not flat. Severe anhedonia, loss of interest, and psychomotor retardation are typically present.

Sexual anhedonia, also known as pleasure dissociative orgasmic disorder, is a condition in which an individual cannot feel pleasure from an orgasm. It is thought to be a variant of hypoactive sexual desire disorder.

Unbidden thoughts are thoughts that come to mind without the subject directly or consciously meaning to think them. Inserted thoughts, while sharing the characteristic of unconsciously or indirectly being conjured, are distinct from unbidden thoughts because of the author of the thoughts. During an experience of unbidden thinking, the subject knows that they are the author of the thought even though they may not have consciously meant to think it. During the feeling of thought insertion, however, the subject feels as though the thought belongs to another person and was inserted into their own mind, making the author of the thought someone other than themselves.

Hyperkinesia, also known as hyperkinesis, refers to an increase in muscular activity that can result in excessive abnormal movements, excessive normal movements, or a combination of both. The word hyperkinesis comes from the Greek "hyper", meaning "increased," and "kinein", meaning "to move." Hyperkinesia is a state of excessive restlessness which is featured in a large variety of disorders that affect the ability to control motor movement, such as Huntington's disease. It is the opposite of hypokinesia, which refers to decreased bodily movement, as commonly manifested in Parkinson's disease. Many hyperkinetic movements are the result of improper regulation of the basal ganglia-thalamocortical circuitry. Overactivity of a direct pathway combined with decreased activity of an indirect pathway results in activation of thalamic neurons and excitation of cortical neurons, resulting in increased motor output. Often, hyperkinesia is paired with hypotonia, a decrease in muscle tone. Many hyperkinetic disorders are psychological in nature and are typically prominent in childhood. Depending on the specific type of hyperkinetic movement, there are different treatment options available to minimize the symptoms, including different medical and surgical therapies.

The first symptoms of neuroleptic malignant syndrome are usually muscle cramps and tremors, fever, symptoms of autonomic nervous system instability such as unstable blood pressure, and sudden changes in mental status (agitation, delirium, or coma). Once symptoms appear, they may progress rapidly and reach peak intensity in as little as three days. These symptoms can last anywhere from eight hours to forty days.

Symptoms are sometimes misinterpreted by doctors as symptoms of mental illness which can result in delayed treatment. NMS is less likely if a person has previously been stable for a period of time on antipsychotics, especially in situations where the dose has not been changed and there are no issues of noncompliance or consumption of psychoactive substances known to worsen psychosis.

- Increased body temperature >38 °C (>100.4 °F), or

- Confused or altered consciousness

- sweating

- Rigid muscles

- Autonomic imbalance

Normally, a human being is able to feel pleasure from an orgasm. Upon reaching a climax, chemicals are released in the brain and motor signals are activated that will cause quick cycles of muscle contraction in the corresponding areas of both males and females. Sometimes, these signals can cause other involuntary muscle contractions such as body movements and vocalization. Finally, during orgasm, upward neural signals go to the cerebral cortex and feelings of intense pleasure are experienced. People who have this disorder are aware of reaching an orgasm, as they can feel the physical effects of it, but they experience very limited or no sort of pleasure.

"Ballism" was defined by Meyers in 1968 as "Repetitive, but constantly varying, large amplitude involuntary movements of the proximal parts of the limbs. This activity is almost ceaseless and movements are often complex and combined". Hemiballismus is usually characterized by involuntary flinging motions of the extremities. The movements are often violent and have wide amplitudes of motion. They are continuous and random and can involve proximal or distal muscles on one side of the body. Some cases even include the facial muscles. It is common for arms and legs to move together. The more a patient is active, the more the movements increase. With relaxation comes a decrease in movements. Physicians can measure the severity of the disorder by having the patient perform a series of basic, predetermined tasks and counting the hemiballistic movements during a set time session. The physicians then rate the patient on a severity scale. This scale gives scientists and clinicians a way to compare patients and determine the range of the disorder.

The name "hemiballismus" literally means "half ballistic", referring to the violent, flailing movements observed on one side of the body.

There are various terms which refer to specific movement mechanisms that contribute to the differential diagnoses of hyperkinetic disorders.

As defined by Hogan and Sternad, “posture” is a nonzero time period during which bodily movement is minimal. When a movement is called “discrete,” it means that a new posture is assumed without any other postures interrupting the process. “Rhythmic” movements are those that occur in cycles of similar movements. “Repetitive,” “recurrent,” and “reciprocal” movements feature a certain bodily or joint position that occur more than once in a period, but not necessarily in a cyclic manner.

Overflow refers to unwanted movements that occur during a desired movement. It may occur in situations where the individual’s motor intention spreads to either nearby or distant muscles, taking away from the original goal of the movement. Overflow is often associated with dystonic movements and may be due to a poor focusing of muscle activity and inability to suppress unwanted muscle movement. Co-contraction refers to a voluntary movement performed to suppress the involuntary movement, such as forcing one’s wrist toward the body to stop it from involuntarily moving away from the body.

In evaluating these signs and symptoms, one must consider the frequency of repetition, whether or not the movements can be suppressed voluntarily (either by cognitive decisions, restraint, or sensory tricks), the awareness of the affected individual during the movement events, any urges to make the movements, and if the affected individual feels rewarded after having completed the movement. The context of the movement should also be noted; this means that a movement could be triggered in a certain posture, while at rest, during action, or during a specific task. The movement’s quality can also be described in observing whether or not the movement can be categorized as a normal movement by an unaffected individual, or one that is not normally made on a daily basis by unaffected individuals.

Postoperative residual curarization (PORC) is a residual paresis after emergence from general anesthesia with neuromuscular-blocking drugs.

Motor disorders are malfunctions of the nervous system that cause involuntary or uncontrollable movements or actions of the body (Stone). These disorders can cause lack of intended movement or an excess of involuntary movement (Mandal). Symptoms of motor disorders include tremors, jerks, twitches, spasms, contractions, or gait problems.

Tremor is the uncontrollable shaking of an arm or a leg. Twitches or jerks of body parts may occur due to a startling sound or unexpected, sudden pain. Spasms and contractions are temporary abnormal resting positions of hands or feet. Spasms are temporary while contractions could be permanent. Gait problems are problems with the way one walks or runs. This can mean an unsteady pace or dragging of the feet along with other possible irregularities (Stone).